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Title: Metal on polyethylene versus metal on metal bearing surfaces in total hip arthroplasty : a prospective randomised study comparing stability, functional outcome, blood metal ion levels and chromosomal aberrations in peripheral lymphocytes
Author: Hanna, S. A.
Awarding Body: UCL (University College London)
Current Institution: University College London (University of London)
Date of Award: 2016
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Despite the high success rates of total hip arthroplasty (THA), there still is no universal agreement amongst hip surgeons regarding the bearing surface of choice. Metal on polyethylene (MoP) bearings have been a popular option since their introduction, but longevity remains a problem due to aseptic osteolysis associated with polyethylene wear particles. Attempts to improve THA longevity and functional outcome have resulted in a renewed interest in metal on metal (MoM) bearings in the last decade. These articulations, however, have been shown to be associated with an unusual mode of failure characterised by tissue necrosis, pseudo-tumour formation and abnormally high blood metal ion levels. The long-term biological implications of the latter remain unknown. This thesis tests the hypothesis that large head (MoM) THAs offer better stability and functional outcome than small head (MoP) THAs, but are associated with increased blood metal ion levels (cobalt and chromium) with corresponding damage in the chromosomes of peripheral lymphocytes postoperatively. A prospective randomised study was set up to compare these variables in two groups of patients (MoP THA) versus (MoM THA). The results demonstrated no difference in stability, range of motion or functional scores up to 3 years post operatively (p > 0.05). Cobalt and chromium blood levels were consistently higher in the MoM group (p < 0.05), but this was not the case with chromosomal aberrations, which were assessed using fluorescent in situ hybridisation (p > 0.05). There was no correlation detected between cobalt & chromium levels and chromosomal aberrations in lymphocytes. In conclusion, orthopaedic surgeons have a choice between different THA materials to implant but there remains no clear indication as to which is the most biocompatible. THA has revolutionised the treatment of arthritis and will continue to be very successful at alleviating pain and restoring function, however, the long-term biological implications of the procedure require further scrutiny.
Supervisor: Blunn, G. ; Briggs, T. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available